Method and apparatus for shipping and storing liquefied gases



Jan. 16, 1951 G. R. BENZ METHOD AND APPARATUS PoR SHIPPING AND s'roRINGLIQUEFIED GAsEs 2 Sheets-Sheet 1 Filed lay 24, 1946 INVENTDR m f me wwQ2 Ma .Q S

ATTORNEY Jan. 16, 1951 G. R. BENZ Ammon AND APPARATUS PoR SHIPPING ANDsToRING LIQUEFIED GASES 2 Sheets-Sheet 2 Filed May 24, 1946 INVEN'TQR'mljgfe if eaz BY A m ATTORNEY Patented Jan. 16, 1951 UNTED STATES'METHOD AND APPARATUS FOR SHIPPING AND STORING LIQUEFIED GASES George R.Benz, Bartlesville, Okla., assigner to Phillips Petroleum Company, acorporation of Delaware Application May 24, 1946, Serial No. 672,141

21 Claims.

This invention relates to an improved method and apparatus for shippingand storing liqueed gases and particularly liquefied gases such asmethane, ethane and ethylene which develop a high vapor pressure undernormal containing tank conditions.

Low vapor pressure hydrocarbons such as propane and butane are normallystored and shipped in pressure tanks or vessels in liquid condition. Inow propose to store and ship high vapor pressure hydrocarbons such asmethane, ethane, ethylene, as well, in liquid form. It is desirable tomaintain such liquefied gases at a reasonably low temperature to avoidexcessive evaporation and vapor pressure build-up within the tank orpressure vessel. While such tanks are often provided with an insulatingjacket, the liquefied gas will nevertheless absorb atmospheric heatthrough the tank walls, creating pressure conditions which require thereease of pressure vapor from the tank if the tank structure is to bemaintained within safe pressure limits.

It has been common practice to discharge these high pressure vapors fromthe tank to the atmosphere through a safety valve when the internalvapor pressure exceeds safe operating limits, as determined byengineering and insurance specifications. The loss of high pressurevapors through the safety valve constitutes a corresponding loss ofvaluable materials which becomes increasingly severe with every degreeof rise in temperature of the tank contents.

As illustrative of the problem, ethane has a vapor pressure of 222 p. s.i. a. at F., a vapor pressure of 350 p. s. i. a. at 32 F., and a vaporpressure of 506 p. s. i. a. at 60 F. Thus it is obvious that if a safepressure condition is to be maintained, the internal temperature of thetank must be controlled so as to keep the vapor pressure of the liquidwithin the desired limits. In most climates the tank contents must becooled by the use of refrigeration equipment associated with the tank,if vapor loss is to be kept down. No practical method or apparatus hasheretofore been provided for refrigerating liquefied gas tanks moving intransit, such as tanks mounted on railroad cars or trucks, and as aresult substantial and serious liquefied gas losses may be encounteredby reason of the necessary release of high pressure vapors to theatmosphere.

In accordance with this invention, the vapor space within the tank istapped and the high pressure vapors conducted to a pressure relief valvewhich opens only when the pressure in the tank vapor space exceeds apredetermined setting,

(Cl. 62-1l say 200 p. s. i. g., which is below the setting of the tanksafety valve. The pressure relief valve is designed to automaticallyopen when the tank pressure exceeds a predetermined setting, and toautomatically close when the pressure drops below a predeterminedsetting. The high pressure vapors Which escape from the automaticallyopened pressure relief valve, ow to a constant pressure valve from whichthe vapors are conducted into a heat interchanger unit mounted in thetank and in heat exchange relationship to the body of liqueed gas. Theconstant pressure valve retains the vapor owing from the valve to theheat interchanger unit at a. substantially conli5 stant pressure ofrelatively low order, of say 0.5

p. s. i. g. The constant pressure valve is designed to automaticallyopen just enough to maintain such constant pressure in the heatinterchanger unit when the constant pressure valve is supplied with highpressure vapors escaping from the pressure relief valve. The reductionin vapor pressure eiected by the constant pressure valve, permitsexpansion of the gas escaping therefrom. The expanding gas of reducedvapor pressure flowing from the constant pressure valve and through theheat interchanger unit, withdraws heat through the heat interchangerwalls from the liqueed gas, and thus reduces the temperature of theliquid. The expanded low pressure vapor leaving the heat interchangerunit is conducted to a point external to the tank and used to providethe driving power necessary to operate a refrigeration unit. Thus theexpanded gas vapor may be used to drive an internal combustion engine orgas motor which provides the power to operate the refrigeration unit, orthe expanded gas may be burned and the heat generated used to operate agas-flame type refrigeration unit.

The refrigeration unit is provided with a circulatory system throughwhich a refrigerant, which may comprise ammonia, Freon, isobutane or thelike, may circulate in a closed system. The circulatory system for therefrigerant includes a heat interchanger unit contained within the tankand in heat transfer relationship with the liqueed gas within the tank.The refrigerant circulating through the heat interchanger unit expandstherein, and in expanding draws heat from the liquefied gas within thetank so as to further o reduce the temperature thereof.

This invention therefore comprehends the provision of a dual-phaserefrigeration system associated with a storage or shipping tank wherebythe high pressure hydrocarbons or liquefied gas U5 is rst cooled by theexpansion of the high pressure vapors withdrawn from the tank, andfurther cooled by a refrigerant supplied by a refrigerating unit drivenor operated by the expanded gas discharged from the first cooling phase.

Thus it will be appreciated that the high pressure vapors normallypermitted to escape to the atmosphere, as is commonly done with liquenedC02 when shipped in tank cars, are used to provide dual-phaserefrigeration of the liqueiied gas without the consumption of otherdriving power. Apparatus to carry out this improved method may be simplein design and can advantageously be associated not only with stationarystorage tanks, but tanks moving in transit.

Other objects and advantages of this invention will become apparent asthe disclosure proceeds within the tank at a point sufliciently low sothat the corresponding vapor pressure of the material will notsubstantially exceed the pressure which the tank has been designed towithstand. The tank would ordinarily be equipped with a vapor line I6having a iiow control valve I6' and,

a liquid line I1 having a flow control valve I1' While thecharacteristic features of this invention will be particularly pointedout in the claims appended hereto, the invention itself and the mannerin which it may be practiced, may be better understood by referring tothe following description taken in connection with the accompanyingdrawings, forming a part thereof, in which Fig. 1 is a diagrammaticillustration of a pressure tank containing liquefied gas of high vaporpressure characteristics, the tank having associated therewith adual-phase refrigeration system. one phase of the cooling system beingoperated directly by the withdrawn high pressure vapors, the secondphase of the cooling system comprising a refrigerating unit andcirculatory system driven by a combustion engine powered by the expandedgases leaving the irst phase of the refrigerating system; and

Fig. 2 is a diagrammatic illustration of a refrigerating system for aliqueiied gas tank having a modiiied second phase cooling system in theform of a gas iiame refrigeration unit powered by the gas vapordischarged from the first phase of the refrigeration system.

Similar reference characters refer to similar parts throughout theseveral views and drawings and specification.

There is diagrammatically illustrated in Fig. 1, a tank III ofcylindrical form commonly used for the storage or transportation ofliquefied gases. It will be appreciated however that this invention maybe associated with any type or form of tank or pressure vessel. Theusual gauging devices, sampling lines, thermometer wells, and the like,are not shown but may or may not be used as desired` Pressure tanks forstorage or ship ment of liquefied gases should be strongly constructedto provide a pressure shell |I built up from steel plate and encasedwithin an insulation 'covering |2.

In filling such pressure tanks with liquefied gas, vapor space I3 shouldbe left above the body of liqueiied gas |4 to provide a chamber forexpansion and space for the gas which evaporates from the body ofliqueed gas, if safe operating conditions are to be maintained. It ispreferable to precool the liquefied gas before loading it into the tank.The pressure of the gas vapor in the vapor space |3 will of coursedepend upon the character of the liquefied gas and the temperature ofthe liquid and the tank interior, the pressure increasingproportionately with the rise in temperature of the liquid. Such tanksare built to safely withstand a certain interior pressure and safeoperation requires that such tanks be equipped with a safety or pressurerelief valve I5 to permit escape of vapors when the vapor through whichthe gaseous or liquid materials are supplied to and withdrawn from thetank.

Transfer of atmospheric heat through the walls of the tank cannot beprevented completely by known methods of insulation, and thereforeliqueiied gas tanks used under normal climate conditions must either bestrong and heavy to an impractical degree to resist the vaporization ofthe liqueed gas, or relief discharge of the pressure vapor must beprovided, or refrigeration must be provided to maintain the interior ofthe tank at a temperature which will insure internal tank pressures notin excess of safe operating, limits.

This invention comprehendslthe utilization of a dual-phase coolingsystem wherein the high pressure vapor is withdrawn from the tankthrough a vapor outlet 20' which leads from the vapor space I3 withinthe tank to an automatic pressure relief valve 20. The valve 2l has anopening and a closing setting which may be adjustably set as theparticular operating condition requires. The opening setting is adjustedto prevent escape of vapor from the vapor space I3 until a certainpredetermined maximum vapor pressure within the space is reached. Whenthe vapor pressure build-up Within the vapor space I3 has reached apredetermined maximum, the pressure relief valve 20 will automaticallyopen, permitting high pressure vapor to ow through a constant pressurevalve 2| and thence to flow at a constant pressure into the outletconduit 22. The high pressure vapor continues to discharge from thepressure relief valve 20 until the vapor pressure in the vapor space I3has been reduced to a predetermined minimum pressure, determined by theminimum pressure setting of the pressure relief valve 20, at which pointthe valve 20 will close.

'Ihus it will be appreciated that the pressure relief valve 20 isadjusted to maximum and minimum settings so as to open when the vaporpressure in the vapor space I3 has risen to a predetermined permittedmaximum, and to close when the vapor pressure is reduced to apredetermined permitted minimum. By way of example, let us assume thatfor a specified tank, a vapor pressure within the tank must not bepermitted to exceed 250 p. s. i. g. The automatic relief valve 20 mightthen be set to open at a maximum setting of 200 p. s. i. g. and set toclose at a minimum setting of p. s. i. g.

The constant pressure valve 2| may be set to open when high pressurevapor ilowing from the pressure relief valve 20 is supplied thereto. Thehigh pressure vapor is permitted to expand in owing through the constantpressure valve 2 I so that the vapor pressure of the vapor dischargedinto the outlet pipe 22 leading from the constant pressure valve 2| isof low order, and in the order of approximately 0.5 p. s. i. g. Theexpansion of y prise a series of coil ,loops as shown in the drawingsthrough which the cold low pressure vapor flows. The cold low pressurevapor in the coil loops withdraws heat from the liqueed gas body I4 andthus eiects cooling of the liquefied gas body |4 in the tank.

The expanded vapor leaves the heat interchanger unit 23 at a pressure ofapproximately 0.5 p. s. i. g. and flows into a pipe 24 leading to acontrol bellows 30 exterior of the tank. The control bellows 30 maybe ofthe Sylphon type designed to operate an electrical switch 3| for thepurpose hereinafter described. The control bellows 30 operates to closethe switch 3| when the vapor pressure supplied to the control bellows 30is increased as a result of the vapor discharged from the constantpressure valve 2|. When the pressure of the vapor flowing to the controlbellows 3|! is substantially reduced, or the vapor flow shut off by theclosed pressure relief valve 20, the control bellows 30 opens the switch3|.

In the illustrative embodiment of the invention shown in Fig. 1, theheated and expanded gas vapor flowing from the contro] bellows 30 feedsinto a gas line 32, into the carburator 33. and thence into the cylinder35 of a gas engine 34. Power to provide starting torque and ignition forthe gas engine 34 is furnished by a storage battery 3B, the terminallines 31 of which are connected in circuit to the electrical switch 3|manipulated by the control bellows 30.

When the circuit switch 3| is closed, current from the battery 36 issupplied to a starting and ignition unit 38. The starting and ignitionunit 38 controls the current ow to a starter motor 39 which may beconnected to the engine fly-wheel 40 by suitable power transmissiongearing 4I. The expanded gas and air mixture supplied by the carburator33 to the gas engine cylinder 35 is ignited by a sparking device 42which is electrically connected to the starting and ignition unit p 38.The starting and ignition unit 38 may be of well known design,constructed to control the current flow to the sparking device 42 and tothe starting motor 39. The starting motor 39 aso has well known devicesassociated therewith for cutting off the current to the starting motor39 and for disconnecting the motor gearing 4| from the engine fly wheel40 when the y wheelhas attained a predetermined driven speed as drivenby the action of the piston in the engine cylinder 35.

It will be appreciated that when the pressure relief valve isautomatically opened in response to tank pressure in excess of thepredetermined maximum, pressure vapor is supplied to the constantpressure valve 2l at a pressure in excess of that desired to operate thepower unit which drives the second phase refrigeration system. Theconstant pressure valve 2| performs the double function of permittingthe vapor to expand, with resultant cooling thereof, and in additionreduces the pressure of the vapor supplied `to the driving unit of thesecond phase refrigeration system to the desirable pressure.

The low pressure vapor supply to the control bellows 30 operates thebellows in a manner so that expansion of the bellows manipulates theswitch 3| into closed position, thereby closing the electrical circuitbetween the current supply battery 36 and the starting and ignition unit38. Both sparking ignition and motor starting torque will then besupplied, and the gas engine will be continuously driven by the expandedgas fed tothe engine carburator 33 from the opened control valveassociated with the control bellows 30.

When thepressure relief valve 20 cuts off the flow of vapor to the heatinterchanger 23, the low pressure vapor to the control bellows 30 willalso cease to flow, causing the control bellows to collapse and open theswitch 3|, thereby cutting oil' the supply of current from the battery36 to the sparking and ignition unit 38.

It will be appreciated that this system could be operated by theelimination of the pressure relief valve 20, in which event the drivingunit would continue in operation to drive the second phase refrigerationunit continuously until the tank was practically empty of liquefied gasand vapor. It is the preferably practice however, to provide the systemwith an automatic relief valve 2D which operates to shut oi the vaporsupply when the tank temperature has been reduced to the point whererefrigeration is not required, and to automatically open the vapor linesWhen more refrigeration is needed.

From the above description it will be appreciated that the high pressurevapor which would normally be permitted to escape to the atmosphere isutilized for rst phase cooling of the liquefied gas through the agencyof the first heat interchanger unit 23, and the expanded gas vapordischarged from the heat interchanger unit 23 is additionally utilizedto drive and operate the gas engine 34. The gas engine 34 may then beusefully employed to drive a compressor 5U forming a part of a secondphase cooling system.

The compressor 5|] may be of any well-known type having a compressioncylinder 5| containing a piston having a suitable driving connection 52with the gas engine 34. Refrigerant supplied to the compression cylinder5|, which may be of any desired type such as Freon, isobutane orammonia, circulates in a closed system and therefore is not lost. Therefrigerant, compressed and reduced to liquid form in the compressioncylmder 5|, ows through outlet pipe 53 into a cooling unit' 54 of lwellknown type to air cool the liquid refrigerant. The cooled liquidrefrigerant flows from the cooler 54 through a constant pressure controlvalve 55 into a discharge line 56 which is in turn connected to a heatinterchanger unit 51 in heat exchange contact with the body of liquefiedgas |4 within the tank |0. The liquid refrigerant expands to vapor-phase as it flows through the heat interchanger unit 51, heat for thispurpose being drawn from the body of liquefied gas |4. The refrigerantin vapor phase leaves the heat interchanger unit 5l with in the tank andis conducted through outlet pipe 58' to the compression cylinder 5| ofthe compressor 50. Thus it will be noted that the refrigerant iscirculated through a closed system which embraces the heat interchangerunit 51, thereby providing a second phase cooling for the liquefied gasWithin the tank lll.

There is shown in Fig. 2 an adaptable and practical modification whereinthe second phase cooling is carried out in a somewhat modifiedrefrigeration system. More particularly, the expanded gas dischargedfrom the control bellows an isconducted into discharge pipe 32 whichleads to a burner 60 associated with a gas type refrigeration unit 6| ofwell known design. The refrigeration unit 6l is connected to a heatinterchanger 51 mounted within the tank by suitable conduits 65 and' 66to provide a closed circulatory circuit for the refrigerant.

Current spark to ignite the expanded gas discharged by the burner 60 issupplied by an igni'- tion element 62' associated with an ignitor unit62 having a circuit'connection with the storage battery 36. A bimetallicthermal switch 64 is also associated with igniter unit B2 and operateswhen heated by the burner name to 'cut off the current supply to theignitor unit 62. Thus when the gas discharged from the burner 60 hasbeen ignited to produce the required name, the heat from the amemanipulates the thermal switch 64 which then in turn throws a switchassociated o with the ignitor unit 62 to render the same inacwill alsooperate to cut ofi the supply of expanded gas to the burner 60,extinguishing the iiame. The bimetallic thermal switch 64 will then cooland return to its normal position. When the flow of expanded gas throughconstant pressure -valve 2| is resumed, the control bellows 30 will opento supply gas to the burner BD and again close the battery switch 3| sothat the ignitor 62 will be energized to ignite the name, and as soon asthe bimetallic thermal switch has again been heated to a predetermineddegree by the name, the thermal switch will de-energize the ignitor unit62.

While the tank, in event of breakdown of the refrigeration system, isdesirably supplied with a safety relieve valve l5 to permit the escapeof vapor Whose pressure is above the maximum pressure setting of thepressure relief valve 2U and near the maximum tank pressure permitted byapplicable regulations. the apparatus lends itself to such sturdyconstruction that breakdown should be rare when periodic inspection andreasonable care of the equipment are provided.

This invention provides a method and apparatus whereby increasedpressure produced by a rise in temperature of a liquefied gas containedin a tank or pressure vessel may be utilized for the purpose of coolingand refrigerating the liquid gas body within the tank in a dual phasecooling operation to effect rapid and economical cooling of theliquefied gas to well within safety pressure limits. The desired coolingis automatically controlled without manual attention or the supply ofexternal power. A practical solution to the problem of cooling liqueedgases having a high vapor pressure so that they may be stored in a lowpressure vessel is thus provided which insures practically no vapor lossto the atmosphere, and which insures highly eiiicient and rapid dualphase cooling automatically controlled by tank pressure conditionswithout manual attention and with a, modest consumption of pressure gas.

This invention is usefully adapted for association with pressure tanksmoving in transit and presents an economical and practical solution tothe problem of transporting high vapor pressure annexed claims. it willbe understood that various omissions, substitutions and changes may bemade by those skilled in the art without departing from the spirit ofthe invention. v

What is claimed is:

1. An improved method for cooling a contained body of liquefied gasnormally volatile under atmospheric temperatures and pressures whichincludes, conducting the pressure vapors released from the containedbody of liquefied gas'into indirect heat interchange relationship withthe contained liquefied gas body under expansion conditions to effectcooling of the contained liqueed gas body, and removing the warmed vaporfrom heat interchange relationship with the contained liqueed gas body.

2. An improved apparatus for cooling'tank contained liquefied gas `ofhigh vapor pressure to insure the retention of tank vapor pressureswithin safe operating limits which includes, a heat interchanger withinthe tank, a conduit connection for conducting pressure vapors from thetank interior to the circulatory system of said heatr interchanger, apressure relief valve for controlling the flow of vapor from the tankinterior to said heat interchanger in accordance with variations inpressure within said tank, and a conduit extending from said heatinterchanger to the tank exterior for discharging the expanded vaporfrom said heat interchanger.

3. An improved apparatus for cooling tank contained liquefied gas ofhigh vapor pressure to ins are the retention of tank vapor pressureswithin safe operating limits which includes, a heat interchanger unitwithin the tank, a conduit connection for conducting pressure vaporsfrom the tank interior to the circulatory system of said heatinterchanger unit, means in said conduit for controlling the expansiono! the high pressure vapors withdrawn from the` tank to supply cold lowpressure vapor to the circulatory system o f said heat interchangerunit, a gas powered refrigeration machine exterior to said tank, asecond heat interchanger unit within said tank operatively connected tosaid 4refrigeration machine to provide a closed circulatory systemthrough which a refrigerant may be circulated, and a conduit connectionextending from said first heat interchanger unit to said refrigerationmachine for suppying the low pressure vapor leaving said iirst heatinterchanger unit to said gas powered refrigeration machine.

4. An improved apparatus for cooling tank contained liqueed hydrocarbonsof high vapor pressure to insure the retention of tank vapor pressureswithin safe operating limits which includes, a heat interchanger unitwithin thev tank, a conduit connection for conducting high pressurevapors from the tank interior to the circulatory system of said heatinterchanger unit, a pressure relief valve for controlling the now ofgas vapor from the tank interior to said heat interchanger unit inaccordance with variations in pressure within said tank, a gas poweredrefrigeration machine exterior to said tank, a second heat interchangerunit within said tank having a closed circulatory` connection with saidrefrigeration machine through which a refrigerant may be circulated, aconduit connection extending from said rst heat interchanger unit tosaid refrigeration machine for supplying the warmed vapor leaving saidrst heat interchanger unit to said gas powered refrigeration machine,and means for automatically controlling the operation of saidrefrigeration machine in accordance with the now of vapor thereto.

5. An improved apparatus for cooling high vapor pressure hydrocarbonscontained within an enclosed tank to insure retention of tank pressureswithin safe operating limits which includes, a heat interchanger withinthe tank, a conduit connection for conducting high pressure vapors fromthe tank interior to the circulatory system of said heat interchanger, apressure relief valve in said conduit for controlling the iiow of gasvapor from the tank interior, a constant pressure control valve in saidconduit operative to permit expansion of the high vpressure vaporsdischarged from said relief valve and discharge thereof into saidcirculatory system in cold condition and at substantially reducedpressure, a refrigeratior unit exterior to the tank designed to utilizegaL vapor as its operating energy, a second heat interchanger withinsaid tank, a conduit system joining said refrigeration unit and secondheat interchanger to provide an enclosed system through which arefrigerant may be circulated, a conduit for conducting the warmed lowpressure vapor leaving said first heat interchanger to said gas poweredrefrigeration unit, allow operated device associated with said conduitconnection, and electrical means operatively connected to said flowoperated device for automatically controlling the operation of saidrefrigeration unit in accordance with the vapor now through said flowoperated device.

6. An improved apparatus for cooling high vapor pressure hydrocarbonscontained within an enclosed tank to insure retention of tank pressureswithin safe operating limits which includes, a heat interchanger withinthe tank, a conduit connection for conducting high pressure vapors fromthe tank interior to the circulatory system of said heat interchanger, apressure relief valve for controlling the flow of gas vapor from thetank interior in accordance with variations in pressure within saidtank, a constant pressure control valve in said conduit operative topermit expansion of the high pressure vapors discharged from said reliefvalve and discharge thereof into said circulatory system in coldcondition and at substantially reduced pressure, a refrigerantcompressor, a driving engine therefore designed to utilize gas as itsoperating energy, a second 'heat interchanger within said tank, aconduit system connecting said refrigerant compressor to said secondheat interchanger to provide an enclosed system through which arefrigerant may be circulated, a conduit for conducting the warmed lowpressure vapor leaving said first heat interchanger to said gas powereddriving engine, a flow operated device associated with said conduitconnection, a storage battery, a starting and ignition unit havingcircuit connection with said storage battery, a circuit switch operablyconnected to said flow operated device for controlling the current flowfrom said battery to said start-` ing and ignition unit in accordancewith the flow of vapor through said flow control device, a sparkingdevice associated with said gas engine controlled by said starting andignition unit, and

fa starting unit' for said engine controlled by said 'starting andignition unit.

7; An improved apparatus forcooling high vapor pressure hydrocarbonscontained within an enclosed tank to insure retention of tank pressureswithin safe operating limits which includes, a heat interchanger withinthe tank, a conduit connection for conducting high pressure gas vaporsfrom the tank interior to the circulatory system of said interchanger, apressure relief valve for controlling the flow of vapor from the tankinterior to said heat interchanger in accordance with variations inpressure within said tank, a constant pressure control valve in saidconduit operative to permit expansion of the high pressure vaporsdischarged from said relief valve and discharge thereof into saidcirculatory system in cold condition and at substantially reducedpressure. a gas type refrigeration unit eX- terior to the tank having agas burner designed to utilize vapor to operate the unit, a second heatinterchanger within said tank, a conduit system connecting saidrefrigeration unit to said second heat interchanger to provide anenclosed system through which a refrigerant may be circulated, a conduitfor conducting the warmed low pressure vapor leaving said first heatinterchanger to said gas burner, a. flow operated device associated withsaid conduit connection, a storage batteryan igniter having a circuitconnection with said storage battery, a circuit switch operablyconnected to said flow operated device for controlling the current owfrom said battery to said igniter in accordance with the ilow of vapor-through said flow operated device, and a thermal element in saidbattery circuit positioned to be heated by the gas flame produced by thegas burner to control the flow of battery current to said igniter.

8, An improved apparatus for cooling tank contained .liquefied gas ofhigh vapor pressure to insure the retention of tank vapor pressuresWithin safe operating limits which includes, a

rconduit connection for conducting pressure vapors from the tankinterior, means in said conduit for controlling the expansion of highpressure vapors withdrawn from the tank to provide a supply of lowpressure vapors, a gas powered refrigeration machine connected to saidlow pressure vapor supply, and a heat interchanger unit within said tankoperably connected to said refrigeration machine to provide a closedcirculatory system through which a refrigerant may be circulated.

9. An improved apparatus for cooling tank contained liquefiedhydrocarbons of high vapor pressure to insure the retention of tankvapor pressures within safe operating limits which includes, a conduitconnection for conducting high pressure vaporsfrom the tank interior, apressure release valve for controlling the flow of gas vapor from thetank interior in accordance with variations of pressure within saidtank, a gas powered refrigeration machine connected to the low pressureside of said pressure release valve, a heat interchanger unit withinsaid tank having a closed circulatory connection with said refrigerationmachine through which a refrigerant may be circulated, and means forautomatically controlling the operation of the machine in accordancewith the flow of the vapor thereto.

10. An improved apparatus for cooling high vapor pressure hydrocarbonscontained within an enclosed tank to insure retention of tank pressureswithin safe operating limits which includes, a conduit connection forconducting high pressure vapors from the tank interior, a presassets l1sure release valve in said conduit for controlling the now of gas vaporfrom the tank interior, a constant pressure control valve in saidconduit operative to permit expansion of high pressure vapors dischargedfrom said release valve at substantially reduced pressure, arefrigeration unit connected to the low pressure side of said pressurecontrol valve and designed to utilize gas vapor as its operating energy,a heat interchanger within said tank, a conduit system joining saidrefrigeration unit and heat interchanger to provide an enclosed systemthrough which a refrigerant may be circulated, a flow operated devicethrough which the low pressure gas is supplied to said refrigerationunit, and electrical means for automatically controlling the operationof said refrigeration unit in accordance with the vapor fow through saidflow operative device.

11. An improved method for cooling a contained body of liquefied gasnormally volatile under atmospheric temperatures and pressures whichincludes, withdrawing high pressure vapor released from the containedbody of liquefied gas, cooling the withdrawn vapor by subjecting thesame to expansion conditions, conducting the expanding vapor into heatinterchange relationship with the liquefied gas body to thereby efl'ectcooling of the liquiiied gas body, removing the warmed vapor from heatinterchange relationship with the liquefied gas body, and automaticallycontrolling the withdrawal of the high pressure vapor in accordance withthe existing vapor pressure overlying the contained body of ,liquefiedgas.

l2. An improved method for cooling tank contained liquefied gasesnormally volatile under atmospheric temperatures and pressures whichincludes, conducting the pressure vapor released from the contained bodyof liquefied gas into indirect heat interchange relationship with thecontained liquefied gas body to thereby effect cooling of the liquefiedgas body, removingthe warmed vapor from heat interchange relationshipwith the liquefied gas body, and automatically controlling thewithdrawal of high pressure vapor from the tank in accordance with the Iexisting pressure conditions in the tank.

13. An improved method for cooling tank contained liquefied gas normallyvolatile under atmospheric temperatures and pressures which includes,withdrawing pressure vapor released from the body of contained liquefiedgas, controlling the withdrawal of the pressure vapor in accordance withthe predetermined pressure conditions in the tank, cooling the withdrawnvapor by subjecting same to expansion conditions, conducting theexpanding vapor into heat interchange relationship with the liqueed gasbody to thereby withdraw sensible heat from the liquefied gas body,withdrawing the warmed low pressure vapor from the tank, and utilizingthe withdrawn low pressure vapor as a supply of power.

14. An improved method for cooling tank contained liquefied gas normallyvolatile under atmospheric temperatures and pressures which includes,withdrawing high pressure vapor released from the body of containedliquefied gas, controlling the withdrawal of the highpressure vapor inaccordance with the existing pressure conditions in the tank, coolingthe withdrawn vapor by subjecting same to expansion conditions,conducting the cooled vapor into indirect heat interchange relationshipwith the liquefied gas body to cool the contained body of liquefied gas,

12 rmaintaining the conducted vapor at a substantially constant lowpressure, withdrawing the warmed low pressure vapor from the tank, andutilizing the withdrawn low pressure vapor as a supply of power tooperate an additional coo system.

15. An improved method for cooling tank contained liquefied gas normallyvolatile under atmospheric temperatures and pressures which includes,maintaining a body of released vapor under pressure over the body ofcontained liquefied gas. withdrawing vapor under pressure from said bodyof vapor, cooling the withdrawn vapor by subjecting the same toexpansion conditions, conducting the cooled vapor into indirect heatinterchange relationship with the liquefied gas body to cool thecontained body of liquefied gas, withdrawing the warmed low pressurevapor from the tank, and utilizing the withdrawn low pressure vapor as asupply of power to operate an additional self contained refrigerationsystem for further cooling the contained body of liquefied gas.

16. An improved method for cooling liquid hydrocarbons normally volatileunder atmospheric temperatures and pressures and contained within anenclosed tank to insure the retention of pressure within the tank withinsafe operating limits which includes, circulating a cooling refrigerantin a closed system in indirect heat interchange relationship with thecontained liquid body to withdraw sensible heat from the containedliquid body and thereby effect cooling thereof and a correspondingreduction of vapor pressure Within the tank, utilizing the vaporwithdrawn from the tank to supply the driving power for the refrigerantcirculating system, and controlling the operation of the refrigerantcirculating system in accordance with the variations in pressure of thetank contained pressure vapor.

17. An improved method for cooling liquid hydrocarbons normally volatileunder atmospheric temperatures and pressures and contained within anenclosed transportation tank to insure the retention of vapor pressureswithin the tank within safe operating limits which includes. maintaininga body of released vapor under pressure over the body of contained fliquefied gas, withdrawing vapor under pressure from said body of vapor,circulating a cooling refrigerant through a closed refrigeration systemin indirect heat exchange relationship with the contained liquid body towithdraw sensible heat from the contained liquid body and thereby effectcooling thereof and a corresponding reduction of vapor pressure withinthe tank, utilizing the vapor withdrawn from the tank to supply thedriving power for the refrigeration circulating system, andautomatically controlling the operation of the refrigerationsystem inaccordance with variations in pressure of the tank contained vapor. I

18. An improved method for cooling liquid hydrocarbons normally volatile'under atmospheric temperatures and pressures and contained within anenclosedtransportation tank to insure the retention of vapor pressureswithin the tank within' safe operating limits which includes,circulating a cooling refrigerant through a closed refrigeration systemin indirect heat interchange relationship with the contained liquid bodyto withdraw sensible heat from the contained liquid body and therebyeffect cooling thereof and a corresponding reduction of lvapor 13pressure within the tank, utilizing the vapor withdrawn from the tank tosupply the power to drive the refrigeration circulating system,automatically controlling the withdrawal of high pressure vapor from thetank in accordance with variations in pressure of the contained pressurevapor, and automatically controlling the starting up and shutting downof the refrigeration system in accordance with the flow of the vaporthereto.

19. An improved method for cooling liquefied gas normally volatile underatmospheric ternperatures and pressures and contained within an enclosedtank to insure the retention of vapor pressures within safe operatinglimits which includes, conducting the vapor released from the .containedbody of liquefied gas through a first cooling system in indirect heatinterchange relationship with the contained liquefied gas body tothereby effect cooling of the tank contained liquefied gas, controllingthe withdrawal of the high pressure vapor from the tank in accordancewith changes in pressure of the tank contained vapor, circulating arefrigerant contained within a second cooling system in heat interchangerelationship with the contained liquid body to y thereby effect furthercooling thereof. and

iirst cooling system in indirect heat interchange relationship with thecontained liqueed gas to thereby eiect cooling of the liqueed gas body,removing the warmed low pressure vapor from heat interchangerelationship with the liquefied gas body, circulating a refrigerantcontained within a second cooling system in heat interchangerelationship with the contained liquefied gas to thereby effect furthercooling thereof, and utilizing the low pressure gas vapor withdrawn fromthe rst cooling system as a source oi operating power for the secondcooling system.

21. An improved method for cooling liquid .hydrocarbonsnormally volatileunder atmospheric temperatures and pressures and contained within atransporation tank to insure the retention of vapor pressures withinsafe operating limits which includes, withdrawing the high pressurevapor from `the tank, conducting the withdrawn vapor through a.firstcooling system in indirect heat interchange relationship with thecontainedliquid body under expansion conditions to thereby effectcooling of the hydrocarbonliquid, removing the warmed low pressure vaporfrom heat interchange relationship with the liquid body, circulating arefrigerant" contained within a second cooling system in heatinterchange relationship with the^ contained liquid body to therebyeiect further cooling thereof, and utilizing the low pressure vaporwithdrawn from the first cooling system as a source of operating powerfor said second coolingfsystem. u

GEORGE R. BENZ.

REFERENCES CITED The following references are of record in the file ofthis patent:

i Number UNITED STATES PATENTS Name i Date 1,354,056 Norton Sept. 28,1920 2,033,094 De Motte Mar.'3, 1936 2,090,163' 1 Twomey Aug.`17, 19372,278,192 Cantacuzene Mar. 31, 1942 2,309,813 Whiting Feb. 2, 19432,327,459 Rice Aug. 24, 1943 2,337,474 Komemann et ai. Dec. 21, 1943

1. AN IMPROVED METHOD FOR COOLING A CONTAINED BODY OF LIQUEFIED GASNORMALLY VOLATILE UNDER ATMOSPHERIC TEMPERATURE AND PRESSURE WHICHINCLUDES, CONDUCTING THE PRESSURE VAPORS RELEASED FROM THE CONTAINEDBODY OF LIQUEFIED GAS INTO INDIRECT HEAT INTERCHANGE RELATIONSHIP WITHTHE CONTAINED LIQUEFIED GAS BODY UNTER EXPANSION CONDITIONS TO EFFECTCOOLING OF THE CONTAINED LIQUE-